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Using High Resolution Site
Characterization to Demonstrate
Monitored Natural Attenuation
Todd Halihan, Ph.D., P.Gp.
©2016 Aestus, LLC 23rd IPEC; Wednesday, November 9, 2016
Todd Halihan, Ph.D., P.Gp.Oklahoma State University/Aestus, LLC
Stuart W. McDonald, P.E.Aestus, LLC
Brian Thomas, P.E.Pastor Behling & Wheeler, LLC
1. MNA vs time and space
2. MNA vs electrical properties
3. Star City, AR
Electrical Evaluation of MNA
– HRSC Process for CSM
– Regulation
4. Questions/Discussion
MNA vs Time – will it go away?
T
A natural oil seep near McKittrick, CA. (Photo: Todd D'Addario) (loe.org)
ORPDOOM
1. Source stopped?
2. Horz and Vert Extent
3. Ecology
4. Presence of degrading microbes
MNA checklist
4. Presence of degrading microbes
What do Electric Glasses See?
1. Biological activity
2. Contamination/
Higher
5
2. Contamination/
Injectates/etc.
3. Groundwater/Fluids
4. Soil/Bedrock Lower
SignalStrength
Electrical View of Microbes
bluetechblog.com/2010/06/15/make-electricity-not-sludge/
Image courtesy of Dr. Estella Atekwana
Electrical Properties of Microbes
Modified fromChe-Alota et al., 2009
Small Microbe House – New Mexico
Gasoline UST Station
Small Microbe House – New Mexico
Dry Sands in Vadose Zone
WeatheredGasoline BlobGasoline Blob
Microbial Subdivision - California
Microbial Subdivision - California
Microbial City - Colorado
Case Study: Pipeline Break, AR
� PSH related impacts generally in finer grained sediment below coarse grained layer
� PSH related impacts limited by lateral extent of coarse grained layer
Case Study: Pipeline Break, AR
coarse grained layer
� Electrical “blob” anomalies crossing the coarse grained layer are targets for PSH related impacts
� No evidence of deep PSH related impacts, just lignite
GeoTrax Survey™ Lines and Wells
“Blob” anomalies crossing the coarse grained layer are targets for PSH related impacts
GeoTrax Surveys Highly Conductive
Data Integration Evaluating Targets
PSH related targets
Coarse grained layer
PSH related impacts bounded by lateral extent of coarse-grained layer
Updated CSM (Graphical Explanation)
N
“Blob” anomalies crossing the coarse grained layer are targets for PSH related impacts
Updated CSM (Graphical Explanation)
Modeled base of coarse layer
PSH mostly in finer grained sediment below coarse layer
In general, low site resistivity w/ low chloride at impacted wells suggests widespread biological activity
Low EC and Cl- at Conductors
� In general, low site ER (w/ low Cl- at impacted wells) suggests widespread biological activity
� Coarse grained layer may act as natural horizontal
Biodegradation:
multiple lines of evidence
� Coarse grained layer may act as natural horizontal “air sparge system” (positive ORP and DO values)
� Microbial activity confirmed with Microbial Insights Petroleum QuantArray
Remedial Design Inputs
• “Blob” anomalies crossing the coarse grained layer
are targets for PSH related impacts
• Multiple lines of evidence indicate PSH degradation
likely ongoinglikely ongoing
• Can material migrate easily?
• Integrative Team looking for Technical Solution– Consultants
– Regulators
– Hydrogeophysicists
– Microbiologists
Key Factors for HRSC MNA
– Microbiologists
• Microbial Patterns Highly Variable
• Iterative Process to Answer Questions
Questions/Discussion
Stuart W. McDonald, P.E.Aestus, [email protected]
Todd HalihanAestus, LLC/Oklahoma State [email protected]
